Dual-quasi BIC enabled plasmonic metasurfaces and active switch between BIC and quasi-BIC

Abstract The potential of local surface plasmon resonance (LSPR) in the aspect of high sensitivity optical sensors has attracted wide attention. Nevertheless, the application of LSPR sensors is limited by material’s inherent ohmic loss and far-field radiation loss, resulting in a lower quality-factor (Q). In this research, a novel all-metal metasurface based on the continuum bound state principle is theoretically designed. Under the conditions of vertical incidence, based on the principle of controlling far-field radiation loss by modifying the structure parameters of metasurface, the metasurface exhibits symmetry protection and Friedrich-Wintgen quasi-bound states in the continuum (quasi-BIC) characteristics, making its Q-factor higher than that of a single quasi-BIC excitation device. The simulation results confirm that the Q-factor of this dual quasi-BIC plasma refractive index sensor can reach about 300, the sensitivity is up to 860 nm RIU −1 , and the figure of merit (FOM) is 43 RIU −1 , another figure of merit (FOM I ) is 85. In addition, it is also realized that the transition between BIC and quasi-BIC states through the design of the graphene-metal boat structure. These research results may bring new application prospects to the fields of biosensing and optical display.